This proposed program represents a multidisciplinary investigation of the behavioral and neurological classification, and the educational remediation, of mental retardation. The disciplines of Experimental Psychology, Pediatric Neurology, Education, Clinical Psychology, and Developmental Psychology are involved. Basic and clinical research will be concerned with the patients at the Walter E. Fernald State School, as well as the mentally retarded in the region of Massachusetts served by the School. Broad objectives are; 1) Development, application, and refinement of methods, in the laboratory and in the field, for the behavioral evaluation and training of severely retarded patients, particularly those who are classified as untestable and/or untrainable: 2) Basic behavioral studies in areas relevant to retardation and to the specific methods with which we are working; 3) Evaluation of neurologic deficit by behavioral techniques, particularly with nonverbal patients for whom the conventional neurologic examination has only limited effectiveness. A major unifying concept, developed experimentally by the senior investigators in their previous work, is that the deficits and retarded children are classifiable as deficits in stimulus-response relations, or attentional processes, and that effective remediation is possible through techniques for establishing elementary and complex forms of stimulus control. The technical development of methods for behavioral shaping, stimulus shaping, and programmed instruction is an important part of the program. An equally important part of the program will be basic studies of discrimination and conceptual learning, crossmodal transfer, and social development. Finally, a Special Rehabilitation Unit will be operated as a "field" setting for the evaluation of laboratory findings.